MXPA01005625A

MXPA01005625A - Method for making polyamide.

Info

Publication number: MXPA01005625A
Application number: MXPA01005625A
Authority: MX
Inventors: Dominique Kayser
Original assignee: Rhodianyl
Priority date: 1998-12-23
Filing date: 1999-12-21
Publication date: 2003-07-14
Also published as: KR100576588B1; BR9917081A; PT1144481E; TWI237040B; US6593448B2; US20020042498A1; AU1784800A; EP1144481A1; RU2243241C2; ATE342932T1; SK9122001A3; PL352320A1; CN1331718A; EP1144481B1; ES2270625T3; MX233714B; WO2000039193A1; CA2356375A1; CN1315911C; FR2787797B1

Abstract

(Co)polyamides, for example the polyamides 6 and 66, are prepared via the improvedly catalyzed polycondensation of (co)polyamide-forming (co)monomers, even in the presence of normally catalyst-inhibiting matting agents (e.g., microparticulate TiO2), the catalyst therefor comprising solid nanometric TiO2 particulates having diameters of less than 100 nm.

Description

POLYAMIDE MANUFACTURING PROCEDURE Description of the invention The invention relates to a process for the manufacture of polyamide. The process is put into operation in the presence of a catalyst. The manufacture of polymers of the polyamide type is mainly carried out by polycondensation from monomers of diacid carboxylic acids and diamines or from compounds of the lactam or amino acid type. These polycondensations can be accelerated by the use of a catalyst. Numerous studies have been provided on, the active catalysts and on their mode of introduction. Among the known catalysts, phosphorus-containing catalysts have been the subject of numerous studies. US patent 39445118 teaches the use of phosphoric acid as a polycondensation catalyst for the manufacture of polyamide 66, this being introduced with the hexamethylenediamine in the polymerization medium. US Pat. No. 4,912,175 teaches the use of phosphonic catalysts, for example of the 2- (2'-pyridyl) -ethylphosphonic acid or 2- (2'-pyridyl) -ethyl-phosphonate diethyl type.

The use of these catalysts makes it possible to increase the polycondensation kinetics of the polyamides. However, phosphorus-containing catalysts are generally almost totally inhibited in the presence of matifying agents, for example coated titanium dioxide. Such agents are in particular used for textile applications in order to decrease the translucency of the fibers, for example for the manufacture of feminine footwear articles. These are generally titanium dioxide compounds on a micrometer scale in proportions ranging from 0.3% to 2% by weight. Micrometric titanium dioxide is chosen for its ease of operation and its whiteness. This is generally incorporated in the polymerization medium at the beginning of the process. This is advantageously passive, for example with the aid of a protective layer, in order to limit the photochemical degradation of the polymer in its presence. The protective layers used are generally based on silica and may contain alumina. The presence of matifying agents and particularly of passive matifying agents strongly decreases the catalytic efficiency of the compounds used to accelerate the polymerizations. The catalyst according to the invention is composed of solid particles based on nanoscale titanium dioxide. By "nanometer", it is understood that the mean diameter of the particles or their average size is less than about lOOnm. The catalyst can be used for the manufacture of all types of polyamides or copolymers based on polyamides. This is, for example, effective for the production of polyamides from the polymerization of lactams or amino acids, co-caprolactam or 6-aminohexanoic acid or for the production of polyamides from the copolymerization between the diacid dicarboxylic and diamine monomers. . This is particularly effective for the catalysis of the condensation of adipic acid and hexamethylenediamine. This is adapted for the manufacture of any composition based on polyamide and any copolymer based on polyamide. According to one embodiment of the invention, the surface of the catalyst based on titanium dioxide is coated with a compound different from titanium dioxide, for example silica. The coating on the surface of the catalyst may not be continuous and may be present on the surface of the particles, for example in the form of clumps. The concentrations used of the catalyst may depend on the state of the surface of the particles and their mode of preparation. These are sold in excess of 100 ppm by weight relative to the weight of the monomer. Polymerizations from diacid carboxylic monomers and diamines generally comprise three steps. The first stage is the concentration of a carboxylate-ammonium di-salt in water, called "N salt." This step is followed by amidation (condensation of the acid functional groups and amines) mainly under pressure. The condensation is then continued under atmospheric pressure to the desired degree of polymerization. This last stage is called finishing. For this type of polymerization the catalyst can be introduced into the N-salt, for example at the time of the high pressure amidification phase. Polymerizations from lactams and amino acids are generally carried out in the following manner: polyaddition of the monomers at a temperature between 200 ° C and 300 ° C. From a mixture of monomer and water, granulation of the product obtained , washing the granules with water for the extraction of the monomers that are low molecular weight portions, and then drying. The catalyst can be, for example, introduced into the monomer and water mixture. The nanoparticular titanium dioxide can be introduced into the condensation reactor either directly in the form of powder, or in the form of suspension or dispersion in a liquid medium. Said liquid medium can be water or a molten polyamide composition. Nanoparticular titanium dioxide catalyzes the polymerization of all polyamide-based compositions. Its use is particularly advantageous when the product manufactured is a composition containing a matting agent. The inhibition of the catalytic effect by the agent is less marked than with a phosphorus-based catalyst. This property is in particular verified in the presence of a mattifying agent based on titanium dioxide of a granulometry of the order of micrometers. For example, the catalyst object of the invention is effective in the presence of titanium dioxide coated, or partially of a compound based on silica, in the state of particles of diameter greater than? Μp ?. The use of the catalyst described herein is particularly advantageous in relation to the use of other catalysts when the proportion of the matifier in the compositions is greater than 0.5% by weight. Other details or advantages of the invention will appear more clearly in view of the examples given below only by way of indication.

Example 1 A suspension of 20% in water of titanium dioxide particles with a diameter of approximately 50 nm, carried out according to the first two stages described in Example 1 of the published patent FR2744914, is introduced in a condensation reactor of Polyamide 66 during the phase of amidification under pressure, so as to obtain in the reactor a catalyst ratio of 500 ppm by weight relative to the polymer. The condensation is carried out at a temperature of 275 ° C. After 45 minutes of finishing, the viscosity index of the polymer obtained is 145 ml / g. An identical procedure performed in the absence of a catalyst leads to a viscosity index of 135 ml / g after 45 minutes of finishing. The viscosity indexes (IV) are measured at 25 ° C with the help of a Ubbelohde-type viscometer for a solution to 5 g / 1 of polymer dissolved in a mixture composed of 90% by weight of formic acid and 10% of water. Example 2 The catalytic efficiency of a catalyst is defined by the difference of the kinetic constants of amidation ki after finishing in the presence and absence of the catalyst relative to the kinetic constant ki in the absence of the catalyst. kicatalisis isin catálisi "Efficiency = kisin catalysis The constant kx is defined by the following system: ki -COOH + -NH2? -CONH + H20 k2 ki -NH-CO- (CH2) 4 -COOH ^ NH2 + C02 + C5H80 The kinetic equations are the following d_ [C00H _] = [-ki [COOH] [NH2] + k2 [CONH] [H20]] [COOH] -k3 [COOH] Dt d [NH2] = [-k1 [COOH] [NH2] + k2 [CONH] [H20]] [COOH] + k3 [COOH] Dt d [CONH] = [ki [COOH] [NH2] -k2 [CONH] [H20]] [COOH] -k3 [COOH] Dt Where [COOH] is the concentration of acid end groups, [NH2] is the concentration of terminal groups amines, [NHCO] is the concentration of amide portions, [H20] is the concentration of water.

[COOH] and [NH2] are measured by potentiometric metering, [H20] is determined from the measurement of the partial pressure in water PH2o in the condensation reactor: log ([H20] / PH2o) = 1800 / T - 1.2214 , where T is the temperature in degrees Kelvin, PH2o is the partial pressure of water in bar and [H20] is the concentration of water in meq / kg, [CONH] is determined by a material balance. A polyamide 66 without matting agent is prepared according to a usual process, in the presence of either the usual phosphorus-comprising catalyst or the catalyst according to the invention. A polyamide 66 is prepared according to the same procedure in the absence of the catalyst. A composition of polyamide 66 is prepared which includes the microparticulate titanium dioxide coated with silica [matifying agent] in a proportion of 1.6% by weight. The catalytic effect obtained is measured with the help of the same catalysts. In relation to the catalytic effect observed in the absence of the matifying agent, a reduction of 95% in the catalytic efficiency of a phosphoric acid in the proportion of 8.4 ppm is observed in the presence of the matifying agent. . For a catalyst composed of titanium dioxide particles with a diameter of approximately 50 nm, partly coated with silica and concentrated at 2000 ppm, prepared according to the four stages of example 1 of published patent FR 2744914, a reduction of the catalytic efficiency of 69%. The catalyst according to the present invention thus sees its action less inhibited than that of a phosphorus catalyst in the presence of a matifying agent.

Example 3 A polyamide 6 is prepared in the absence and in the presence of the catalyst. The catalyst used is nanoparticular titanium dioxide treated with silica, prepared according to the four steps of Example 1 of published patent FR2744914. The polymerization process is as follows: a mixture of 70% by weight of caprolactam and 30% by weight of water is concentrated by heating 80% by weight of caprolactam. The concentrated mixture is brought to a pressure of 17.5 bar and distilled at this pressure. The product obtained is retained at atmospheric pressure and is finished at 270 degrees C. The catalyst is introduced in a proportion of 2000 ppm by weight relative to the polymer in the initial mixture of caprolactam and water.

In the absence of the catalyst, the viscosity after finishing is 130 ml / g. In the presence of the catalyst, the viscosity after finishing is 145 ml / g.

Claims

CLAIMS 1. A process for the manufacture of polyamides, characterized in that the polymerization is catalyzed by solid particles based on titanium dioxide of a diameter less than lOOnm.
2. The process according to claim 1, characterized in that the titanium dioxide particles with a diameter of less than 100 nm are at least partially coated with another compound.
3. The process according to claim 2, characterized in that the titanium dioxide particles of less than lOOnm diameter are at least partially coated with a silica-based compound.
4. The process according to any of claims 1 to 3, characterized in that the concentration of the catalyst is greater than 100 ppm.
5. The process according to any of claims 1 to 4, characterized in that the polyamide contains a matifying agent.
6. The process according to claim 5, characterized in that the mattifying agent contains titanium dioxide in the form of particles with a diameter greater than 1 μp ?.
7. The process according to claim 6, characterized in that the particles of titanium dioxide with a diameter greater than 1 μm are at least partially coated with a compound based on silica and / or alumina.
8. The process according to any of claims 5 to 7, characterized in that the matifying agent is present in the polymer at a proportion of 0.5% by weight.
9. The process according to any of claims 1 to 8, characterized in that the polyamide is the polymerization product of a lactam or an amino acid.
10. The method according to claim 9, characterized in that the lactam is caprolactam.
11. The process according to any of claims 1 to 8, characterized in that the polyamide is a condensation product of diacid carboxylic monomers and diamines.
12. The process according to claim 11, characterized in that the polyamide is for the most part composed of the condensation product between adipic acid and hexamethylenediamine.
13. The process according to any of claims 11 to 12, characterized in that the catalyst is introduced into the mixture of the carboxylate-ammonium di-salt and water.
14. The process according to claim 13, characterized in that the catalyst is introduced under the concentrated form of a liquid medium.
15. The method according to claim 14, characterized in that the liquid medium is water.
16. The method according to claim 14 characterized in that the liquid medium a molten polyamide composition.